Hi! I'm having a problem when trying to export my model as an FMU.

The problem appears when trying to export and reads as:

"[6] 15:52:39 Symbolic Error
[C:/OM117/OM32bit/OMCompiler/Compiler/BackEnd/Differentiate.mo: 265:5-265:157]: Derivative of expression "vol.dynBal.medium.u = vol.ports[3].h_outflow - pressure_Fluegas / vol.dynBal.medium.d" w.r.t. "time" is non-existent.

[7] 15:52:39 Translation Error
[Modelica.Media.Air.ReferenceAir: 160:9-160:20]: Internal error
Differentiate.differentiateEquationTime failed for vol.dynBal.medium.u = vol.ports[3].h_outflow - pressure_Fluegas / vol.dynBal.medium.d

[8] 15:52:39 Translation Error
Internal error - IndexReduction.pantelidesIndexReduction1 failed! Use -d=bltdump to get more information.

[9] 15:52:39 Translation Error
Internal error - IndexReduction.pantelidesIndexReduction failed!

[10] 15:52:39 Translation Error
Internal error Transformation Module PFPlusExt index Reduction Method Pantelides failed!"

I think this has something to do with the fact that I'm using a real input ("pressure_Fluegas") to set a pressure in the boundary since when I set "use_p_in" to false at the boundary and remove my real input, I can export the model without any errors..

I have attached the model down below if anyone can have a look at it.
Model.mo